This invention relates to testing and characterization of microwave high power transistors and amplifier chips (device under test, DUT); the test system disclosed here allows for high volume, high speed production testing chips on wafer through acquisition and processing of its RF characteristics, typically gain, output power, efficiency, inter-modulation etc, under precise source and load impedance at the fundamental and harmonic frequencies (see ref. 1) corresponding to meaningful reflection factors |Γ|≦1.